How to iterate over alternative elements using an iterator?

Randhir :

List<Integer> list = Arrays.asList(1, 2, 3, 4, 5, 6);
Iterator<Integer> it = list.iterator();
while (it.hasNext()) {
    System.out.println(it.next());
}

The above code will iterate sequentially 1 through 6. Can we iterate the same list alternatively so that it will print 1, 3, 5 without changing the while loop?

daniu :

Create your own Iterator.

class SkippingIterator<T> implements Iterator<T> {
    private List<T> list;
    private currentPosition;
    private int skipBy;
    public SkippingIterator(List<T> l) {
        this(l, 2);
    }
    public SkippingIterator(List<T> l, int skip) {
        this(l, skipBy, 0);
    }
    public SkippingIterator(List<T> l, int skip, int startPosition) {
        list = l;
        skipBy = skip;
        currentPosition = startPosition;
    }
    public boolean hasNext() {
        return currentPosition < list.size();
    }
    public T next() {
        T result = list.get(currentPosition);
        currentPosition += skip;
        return result;
    }
}

making your code

List<Integer> list = Arrays.asList(1,2,3,4,5,6);
Iterator it = new SkippingIterator<>(list);
while(it.hasNext()){
    System.out.println(it.next());
}

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